Conventionally, there has been known an elastomeric sealing device that seals an annular gap between two members configured to be reciprocally movable relative to each other. Such a sealing device is used in such a manner that it is fitted in an annular fitting groove formed on one of the two members so that it slides on the other member. As examples of such a sealing device, a so-called D ring having a D-shaped cross section and a rectangular ring having a rectangular cross section with an annular convex portion formed on its sliding side are known. (refer to a first patent literature).
In such sealing devices, especially in cases where a sealing device has a large inside diameter, in terms of cost or manufacturing efficiency, it is advantageous to manufacture individual sealing devices by conducting a parting operation to one molded body, rather than molding individual sealing devices separately.
However, in the case of a sealing device in which an annular convex portion is formed on an inner peripheral side thereof, when the above-mentioned parting operation is to be conducted, it is difficult to recognize the position of the annular convex portion. Therefore, there is a problem that it is difficult to achieve a high positioning accuracy of the parting operation (refer to a second patent literature).
In addition, in the case of a sealing device such as a D ring mentioned above, there is also a disadvantage that its sliding resistance tends to become high because the main body portion of the sealing device is constrained in the fitting groove and thereby making it difficult for the ring to deform.